This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Vitamin B-12 deficiency is a common problem that affects the general US population and the elderly in particular. The elderly are at risk for preclinical vitamin B-12 deficiency due to the increased presence of B-12 malabsorption and atrophic gastritis as a consequence of aging. The deficiency of vitamin B-12 in the elderly has potentially serious complications including dementia, Alzheimer?s disease, and cancer. Current approaches to diagnosing B-12 deficiency are inadequate because they lack specificity, have poorly defined reference ranges or are expensive. Our proposed test, known as the B-12 Breath Test-BBT, will have the advantage of being non-invasive, be easy to administer and have a long shelf life. The BBT will allow physicians to accurately test for B-12 deficiency. Our goal is to identify vitamin B-12 deficiency in a preclinical stage when treatment can avert complications. Diagnosing this deficiency is meaningful because it can be effectively and inexpensively treated with appropriate vitamin B-12 supplementation. The underlying scientific principle of the test is that the metabolism of propionate is limited by the availability of vitamin B-12. After orally administering a tracer dose of 13C-non-radioactive, labeled propionate, the amount of 13CO2 is reduced in the breath of vitamin B-12 deficient individuals. The phase I grant demonstrated the feasibility of this concept. In Phase II we will refine the testing procedure and simplify the test. We will examine a smaller dose of propionate, a single 20-minute breath collection and eliminate the need to be in a fasted state for greater than 1 hour.